Blow molded article of thermoplastic material having a threaded insert therein

ABSTRACT

A method of and apparatus for blow molding an article having an insert permanently affixed thereto. The insert is placed on a removable member insertable through a wall of a mold section for positioning the insert in spaced relation to a mold cavity wall. An extruded parison is fed between complementary mold sections which are closed about the parison for enclosing a portion of the same. Air is introduced into the enclosed parison to expand the same into conformity with the cavity defined by the mold sections and the insert. Plastic material flows into the spacing between the insert and mold cavity wall to partially encapsulate the insert in sealed, interlocked relation to the wall of the plastic article.

[451 July 3,1973

United States Patent Confer et al.

[ BLOW MOLDED ARTICLE OF 1,529,044 3/1925 Willard THERMOPLASTIC MATERIALHAVING A 3 fillackman [75] Inventors: Raymond C. Confer, (giasport,N.Y.; primary Examiner george Lowrance Floyd Talmon, Falrvlew ParkAssistant Examiner-Stephen P. Garbe Ohlo Att0rney-Christel & Bean [73]Assignee: Air-Lock Plastics,Inc.,Tonawanda,

[57] ABSTRACT A method of and apparatus for blow molding an article [22]Filed:

Mar. 23, 1-970 having an Insert permanently affixed thereto. The in-Appl- N03 21,944 sert is placed on a removable member insertable througha wall of a mold section for positioning the in- 5 sert in spacedrelation to a mold cavity wall. An extruded parison is fed betweencomplementary mold sections which are closed about the parison forenclosing a portion of the same. Air is introduced into the enclosedparison to expand the same into conformity with wMmA- BIMHL m s 2 7 653/ i 4 5 u 2 NW3 "7 ""2 W22 ""7 m2 mml U7 "2 Mn m mz mm; m w MN C 8 LMME 1.] 18 55 ll Plastic material flows into the spacing between theinsert and mold cavity wall to partially encapsulate the insert insealed, interlocked relation to the wall of the plastic article.

[56] References Cited UNITED STATES PATENTS 264/275 /310 X 4 Claims, 8Drawing Figures 2,338,827 1/1944 Teague et al. 3,204,959 9/1965Nicholls.........r 3 325,031 6/1967 BLOW MOLDED ARTICLE OF THERMOPLASTICMATERIAL HAVING A THREADED INSERT THEREIN BACKGROUND OF THE INVENTIONThe present invention relates generally to the blow molding ofthermoplastic material and, more particularly, to a method of andapparatus for blow molding plastic articles having inserts permanentlyaffixed thereto while maintaining the integrity of the wall surfaces ofthe article.

In molded plastic articles, such as storage tanks, containers and thelike, it is sometimes desirable to provide inserts, such as fittings,sockets, nuts and the like, in the walls of these plastic articles forattaching the same to other support structure or for connecting valves,hose and conduit couplings or other members thereto. Conventionally,these inserts are fitted into the plastic article after it has beenformed by pinning the insert therein or by employing separable fastenersto secure the inserts in place. Not only is this a time-consuming andexpensive procedure requiring a number of parts, but the wall surfacesof the plastic article are necessarily punctured and pierced, therebyinterrupting the integrity of such wall surfaces. Providing andmaintaining a fluid-tight seal about the insert presents a problem.Also, a problem is encountered in rigidly affixing these inserts to thewall surfaces in order to preclude displacement or removal of suchinserts from their original positions.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an improved method of molding plastic articles having insertspermanently affixed thereto while maintaining the integrity of thearticle walls.

It is another object of the present invention to provide an improvedapparatus for molding plastic articles into shape having insertspermanently affixed thereto and interlocked therewith as an integralpart of the finished article.

It is a further object of the present invention to provide the foregoingapparatus with means for releasably mounting and positioning insertsthereon prior to the molding operation.

The foregoing and other objects, advantages, and characterizing featuresof the present invention will become clearly apparent from the ensuingdetailed description thereof, considered in conjunction with theaccompanying drawings wherein like reference numerals denote like partsthroughout the various views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of anillustrative plastic molded article formed by the method and apparatusof this invention;

FIG. 2 is a fragmentary, vertical sectional view taken through the upperportion of a mold assembly of this invention;

FIG. 3 is a fragmentary, vertical sectional view taken through the lowerportion of a mold assembly of this invention;

FIGS. 4 and 5 are schematic views illustrating the mold parts of thisinvention relative to different positions of the tubular parison;

FIG. 6 is a schematic layout of a complete apparatus of this invention;

FIG. 7 is a fragmentary sectional view through a portion of the wall ofa molded plastic article showing one type of insert permanently affixedthereto; and

FIG. 8 is a view similar to FIG. 7 but illustrating another form ofinsert.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to theaccompanying drawings, there is shown apparatus of this invention forproducing hollow plastic articles, especially containers, having insertsintegrally formed therewith. One illustrative form of article producedby the method and apparatus of this invention is a container, generallydesignated 10 and shown in FIG. 1. Container 10 is of a unitary,one-piece construction, formed of a thermoplastic material, such aspolyethylene for example, and comprises a front wall 12, a rear wall 14,opposite side walls 16 and opposite end walls 18. Although container 10of the illustrative embodiment is of a generally flat, rectangularlyshaped configuration, it should be understood that such container cantake various shapes and sizes and have protrusions and/or recessesembossed on any of the walls, as desired.

A plurality of inserts 20 are mounted in front wall 12. These insertsmay take any form, such as pipe fittings, nuts, washers, fasteners ofany suitable type, or any combination of these, the specific insertemployed being dictated by the particular application of the finishedarticle. In the embodiment illustrated in FIG. 1, inserts 20 are nutsfor receiving bolts used to attach a metal plate to the outer flatsurface of front wall 12.

In accordance with the present invention, inserts 20 are moldedintegrally with container 19 by a blow molding technique as follows:

With reference to FIGS. 4-6, a molten plastic material, such asplasticized polyethylene for example, is fed into an extrusion die 22 byconventional feed means, not shown, from a suitable supply 24 (FIG. 6).The molten plastic material is extruded from die 22 as a tubular parison26 of a laterally elongated, flat-sided form approximating the shape ofthe container to be molded. parison 26 is gravity fed downwardly betweenmold sections 28 and 30 which are mounted for movement into and out ofengagement about parison 26. Mold sections 28 and 30 can be -pivotallymounted or otherwise supported and can be moved by conventional drivemeans 32. The free end of parison 26 is disposed below the lower ends ofmold sections 28 and 30 before such sections engage parison 26 to insurethat the enclosed portion of parison 26 extends from the top to thebottom of said mold sections 28 and 30.

Mold sections 28 and 30 are provided with cavities 34 and 36,respectively, (FIGS. 2 and 3). When mold sections 28 and 30 are engaged,cavities 34 and 36 form a mold cavity defining the outer surfaceconfiguration of the finished container 10.

Mold section 28 is provided with a plurality of apertures 38 (only oneis shown in FIGS. 2 and 3) through which are inserted removable pins 40having studs 42 projecting axially from the free ends thereof into themold cavity. Inserts 20 are positioned on studs 42 prior to the moldclosing operation. Pins 40 extend slightly inwardly of the mold cavitywall and have faces 41 against which inserts 20 abut. Thus, a clearancespace approximating the wall thickness of the finished article isprovided between insert 20 and the mold cavity wall.

FIG. 3 illustrates a pin 40 of a larger diameter than pin 40 having astud 42' of a different size and configuration from stud 42. The sizesand shapes of pins 40,

40' and studs 42, 42 can vary within the purview of this invention, asdictated by the particular type of insert provided. Also, it should beunderstood that any desired number of apertures 38 and pins 40 arrangedin any suitable pattern can be provided in either mold section, or bothmold sections, as desired.

in the particular embodiment illustrated in FIGS. 2 and 7, insertcomprises a nut having a generally annular flange 44, a pair of stepped,indented portions 46 and 48, and an inner portion 50 having a peripheralpolygon surface 52 projecting laterally outwardly of portion 48 to formbetween portions 46 and 52 an annular recess 54 for receiving moltenplastic material therein to form a mechanical locking ring 56. Duringthe molding operation, molten plastic material also flows about aportion of the outer surface of flange 44 between it and cavity wall 34forming an outer mechanical locking ring 57 to further secure insert 20in place. The plastic material disposed about polygon surface 52 alsoforms a mechanical lock preventing rotation of insert 20 within itsplastic sheathing. A threaded bore 58 extends axially into the body ofinsert 20 for receiving a suitable bolt.

Insert 20', shown in FIGS. 3 and 8, comprises a nut having a bodyportion 60 provided with a threaded bore 62. A circular flange 64projects laterally outwardly from body portion 60 and is provided with aseries of conical projections 66 struck out of flange 64 to formcorresponding depressions 68 therein. Also, a series of openings 70extend through flange 64. During the molding operation, molten plasticmaterial flows into depressions 68 and into and through openings 70 andabout projections 66 to provide a mechanical lock securing insert 20' inplace. Also, molten plastic material flows about a peripheral portion ofthe outer surface of flange 64 between it and cavity face 34 forming anouter mechanical locking ring 71 to further secure insert 20' in placeand prevent axial displacement or removal thereof.

Mold section 30 is provided with a knife-edge formation 72 extendingcompletely around mold cavity 36 and is adapted to engage against moldsection 28, which serves as a bed plate, for severing and enclosing aportion of parison 26. If desired, mold section 28 can be provided witha knife-edge formation rather than mold section 30 or both mold sections28 and 30 can have knife-edge formations which engage to severe aportion of parison 26. Thus, upon closing of mold sections 28 and 30about parison 26, a portion thereof is severed and enclosed within moldsections 28 and 30.

Mold section 28 carries means for introducing expansion fluid into theenclosed parison portion, such means comprising a needle 74 which ismounted in section 28 and projects inwardly of the cavity defining facethereof through the wall of the enclosed parison. A source of compressedair 76 is connected via conduit 78 to needle 74 for introducingcompressed air into the enclosed, hollow parison expanding the same intoengagement with the mold cavity walls, causing the enclosed parison toassume the shape of the cavity as shown in FIGS. 2 and 3. Thethermoplastic material also flows about the entire body portion of theinserts to completely encapsulate or encase the same with a sheet ofthermoplastic material. As shown in FIGS. 7

and 8, the thermoplastic material flows into recess 54 of insert 20 andinto depressions 68 and openings of insert 20'to lock such insertswithin the wall of the finish article. Also, the thermoplastic materialflows around flanges 44 and 64 up to removable pins 40 and 40' tofurther lock the inserts in place.

Mold sections 28 and 30 are then cooled, as by means of cooling waterducts 80 connected to a suitable source of cooling water 82. This coolsand sets the molded plastic, causing it to retain the moldconfiguration. After the plastic material has set sufficiently to becomeself-supporting, pins 40 and 40' are removed providing access openingsto inserts 20 and 20'. Mold sections 28 and 30 are opened leaving thefinished article with inserts 20, 20' permanently affixed thereto whilemaintaining the wall integrity of the finished article. The containerwall, being continuous, is just as fluid tight as though the insert werenot therein. The outer wall surface of container 10 remainssubstantially continuous while the inserts are somewhat recessed fromthe plane of the container wall and permanently sealed therein.

In order to maintain the plastic material of parison 26 within moldsections 28 and 30 in a molten, semi-fluid condition prior to cooling,mold sections 28 and 30 are heated by heating elements (not shown)enclosed in the walls of mold sections 28 and 30 and connected to asuitable heat source 84 via line 86. In this manner, the enclosedparison is maintained at or near its plasticizing temperature tofacilitate the expansion thereof against the mold cavity walls and toaid in the pinching and severing of the enclosed parison withoutrequiring special cutting equipment or excessive forces to cut through acooled plastic.

If desired, a vacuum source 88 can be connected to mold sections 28 and30 via conduit 90 to withdraw air from between the enclosed parison andthe cavity walls of mold sections 28 and 30. A strong suction force isnot necessary, and mere venting often will suffice. The section force ismerely to relieve the pressure of any air that might be trapped betweenparison 26 and the cavity walls of mold sections 28 and 30, whichtrapped air would tend to prevent the parison from following the contourof cavities 34 and 36 of mold sections 28 and 30 engaged about parison26. The passages establishing communication with the mold sectioncavities 34 and 36 are so small as to preclude the admittance of moltenthermoplastic material therein, while being sufficient to permit thedesired withdrawal of air. Such withdrawal takes place as mold sections28 and 30 close about the extruded parison 60 prior to the introductionof expansion fluid through needle 74. The introduction of expansionfluid into the enclosed parison causes the same to expand intoconformance with the cavity wall defining surfaces of mold sections 28and 30. Undesirable inward collapsing of the parison wall is avoided bythe force of the expansion fluid and the elimination of air betweenparison 26 and mold sections 28 and 30.

The feeding of the raw plastic material into extrusion die 22, theparison extruding operation, the opening and closing of mold sections 52and 54 and the heating and cooling thereof, the withdrawal of air frombetween parison 26 and the cavity walls of mold sections 52 and 54, andthe introduction of expansion fluid all are controlled in a timedrelationship by suitable programming or control means 92. Since suchcontrols are conventional, in and of themselves, they are onlyschematically shown in FIG. 6 and it is believed that no furtherdescription or amplification is necessary. Indeed, the entire showing inFIG. 6 is schematic only.

Although the plastic material used in the above described moldingoperation preferably is polyethylene, it should be understood that anysuitable thermoplastic material can be used, as desired. Also, asearlier mentioned, this invention is not restricted to a method of andapparatus for forming a container as shown in FIG. 1 nor limited to theparticular inserts shown in the drawings, but has utility in forming anyconfigurated plastic article to which it is desired to permanently affixany suitable insert.

It should be noted that a similar type mold but of lesser thickness,employing removable pins 40, 40' to temporarily mount inserts thereon,an be used to produce plastic molded articles by a technique known asrotational molding whereby a heated mold is rotated to disperse aplastic material injected into themold in powder form against the wallsof the mold cavity. As the powdered plastic material engages the heatedmold cavity walls, it melts and adheres thereto to form a uniform layerof plastic material about the cavity defining walls.

From the foregoing, it is apparent that the objects of the presentinvention have been fully accomplished. As a result of this invention,an improved method and apparatus is provided for molding a plasticarticle into shape and permanently affixing inserts thereto in aninterlocked relation with such plastic article while maintaining thewall integrity of the finished article.

Specific forms of this invention having been described in detail, it isto be understood that this has been done by way of illustration only.

We claim:

l. A plastic article comprising a hollow body having a wall ofthermoplastic material and at least one attaching insert permanentlymounted in said wall in recessed relation to the outer surface thereof,said insert having a body projecting inwardly into said hollow body anda laterally projecting flange adjacent the outer end of said insertbody, the thermoplastic material of said wall overlying a portion of theouter surface of said flange and forming a mechanical locking portionpreventing removal of said insert, said insert body having a threadedbore opening through said outer end thereof and said mechanical lockingportion of said wall having an access opening therethrough to said bore,the thermoplastic material of said wall also extending about said flangeand said insert body inwardly of said flange in a manner completelyencapsulating said insert body except for said access opening andthereby maintaining the integrity of said wall with said insertpermanently sealed therein, said insert having means coacting with thematerial of said wall to provide a mechanical interlock preventingrotation of said insert relative to said wall.

2. A plastic article according to claim 1 wherein said last-named meanscomprise openings in said flange for receiving thermoplastic materialtherein.

3. A plastic article according to claim 1, wherein said article is acontainer having a body of unitary one-piece construction and apluralltY of such attaching inserts permanently mounted in a wallthereof.

4. A plastic article according to claim 1 wherein said last-named meanscomprises a polygonal configurated surface about a portion of saidinsert body preventing rotation of said insert within said thermoplasticmaterial encapsulated about said body.

II I t

1. A plastic article comprising a hollow body having a wall ofthermoplastic material and at least one attaching insert permanentlymounted in said wall in recessed relation to the outer surface thereof,said insert having a body projecting inwardly into said hollow body anda laterally projecting flange adjacent the outer end of said insertbody, the thermoplastic material of said wall overlying a portion of theouter surface of said flange and forming a mechanical locking portionpreventing removal of said insert, said insert body having a threadedbore opening through said outer end thereof and said mechanical lockingportion of said wall having an access opening therethrough to said bore,the thermoplastic material of said wall also extending about said flangeand said insert body inwardly of said flange in a manner completelyencapsulating said insert body except for said access opening andthereby maintaining the integrity of said wall with said insertpermanently sealed therein, said insert having means coacting with thematerial of said wall to provide a mechanical interlock preventingrotation of said insert relative to said wall.
 2. A plastic articleaccording to claim 1 wherein said last-named means comprise openings insaid flange for receiving thermoplastic material therein.
 3. A plasticarticle according to claim 1, wherein said article is a container havinga body of unitary one-piece construction and a plurality of suchattaching inserts permanently mounted in a wall thereof.
 4. A plasticarticle according to claim 1 wherein said last-named means comprises apolygonal configurated surface about a portion of said insert bodypreventing rotation of said insert within said thermoplastic materialencapsulated about said body.